The invention relates to a heat exchanger, in particular for motor vehicles, having a large number of flat tubes through which a fluid cooling medium can flow, and having corrugated fins which are associated with these flat tubes and to which environmental air or other media can be applied.
EP 0 030 072 B1 discloses such a heat exchanger. The heat exchanger comprises a large number of flat tubes, through which coolant can flow, as well as corrugated fins which are associated with these flat tubes and to which environmental air can be applied. In this case, the flat tubes have indentations, with a very small indentation height. The indentations point inward on the flat faces of the tubes and are used to increase the robustness of the flat tubes. A heat exchanger such as this has the disadvantage that the coolant forms a hot core flow layer or stream within the flat tubes. This hot core flow is insulated from the flat tube walls by a cooler wall flow layer and exchanges little heat. As a result the amount of heat transferred between the core flow and the flat tube walls is low.
DE 196 54 367 A1 is mentioned here but is not believed to relate to the same field of use as the present invention. It discloses a rectangular tube for an exhaust gas heat exchanger equipped with elongated vortex generators that point inward in the form of winglets. The vortex generators, which are each arranged in pairs in a V-shape, are formed from the solid material of the tube and are positioned such that they diverge in the main exhaust gas flow direction. The vortex generators are used to reduce deposits on the inner walls of the tubes of solids—such as carbon black—contained in the exhaust gases. No further details are given of the dimensions of the vortex generators.
In accordance with another aspect of the present invention, there has been provided a heat exchanger for motor vehicles comprising (a) a plurality of flat tubes through which a fluid cooling medium can flow, (b) elongated vortex generators in the form of indentations pointing inward on at least one flat face of said flat tubes and (c) corrugated fins to which environmental air and other media can be applied, operably linked to said flat tubes. The ratio between a height, h, of the vortex generators and a height, H, of the flat tubes is approximately 0.05 to 0.5. The longitudinal axes of the vortex generators are inclined at angles of approximately 10° to 40° with respect to the tube longitudinal axis. The vortex generators which are adjacent to one another transversely with respect to the longitudinal axis of the tube are inclined in opposite directions. The flat tubes are beaded tubes, with a bead running parallel to the tube longitudinal axis.